This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present disclosure that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Conventional image capture devices render a three-dimensional scene onto a two-dimensional sensor. During operation, a conventional capture device captures a two-dimensional (2-D) image representing an amount of light that reaches each point on a sensor (or photo-detector) within the device. However, this 2-D image contains no information about the directional distribution of the light rays that reach the sensor (may be referred to as the light-field). Depth, for example, is lost during the acquisition. Thus, a conventional capture device does not store most of the information about the light distribution from the scene.
Light-field capture devices (also referred to as “light-field data acquisition devices”) have been designed to measure a four-dimensional (4D) light-field of the scene by capturing the light from different viewpoints of that scene. Thus, by measuring the amount of light traveling along each beam of light that intersects the sensor, these devices can capture additional optical information (information about the directional distribution of the bundle of light rays) for providing new imaging applications by post-processing. The information acquired/obtained by a light-field capture device is referred to as the light-field data. Light-field capture devices are defined herein as any devices that are capable of capturing light-field data.
Light-field data processing comprises notably, but is not limited to, generating refocused images of a scene, generating perspective views of a scene, generating depth maps of a scene, generating extended depth of field (EDOF) images, generating stereoscopic images, and/or any combination of these.
Among the several existing groups of light-field capture devices, the “plenoptic device” or “plenoptic camera”, embodies a microlens array positioned in the image focal field of the main lens, and before a sensor on which one microimage per microlens is projected. In the following description, the area of the sensor on which one (or several) microimage is targeted to be projected is referred to as “microimage area” or “sensor microimage” or “microimage of the sensor” or “exposed zone” or “zone of projection”. The raw image of the scene obtained as a result is the sum of all the pixels of the sensor belonging to one sensor microimage and/or another. The angular information of the light-field is then given by the relative position of pixels in the microimage areas with respect to their center. Based on this raw image, the extraction of an image of the captured scene from a certain point of view, also called “demultiplexing”, can be performed. The demultiplexing process can be seen as a data conversion from the 2D raw image to the 4D light-field. The resulting demultiplexed light-field data can be represented by a matrix of views in which all the views are horizontally and vertically aligned.
Regarding colors detection, pixels of a majority of sensors just record the quantity of visible photons passing through them, regardless their colors. In order to acquire a colored 4D light-field data, it is know from background art to mount a Color Filter Array (CFA) on top of the sensor. For instance, Bayer filters which cover 2 by 2 pixels with the three distinct colors Red (R) Green (G) Blue (B) located in the following order R, G, G, B within the 2 by 2 matrix, are commonly used as CFA. However, a skilled person will understand that the expression “Color Filter Array” as used in the following description does not only refer to Bayer filters but also to all the alternative CFA of the art.
One main drawback of this technology is that it is lowering the light sensitivity of the sensor, since at least half of the photons are blocked by the CFA. In addition, chromatic aberrations may occur on the edges of the sensor microimage and therefore affect the quality of the rendered image. In an attempt to solve these problems, patent document US2014/0146201A1 discloses a CFA that only covers a portion of a sensor microimage. However, it is not sufficient to improve the light sensitivity of the sensor.
It would hence be desirable to provide a sensor that shows improvements over the background art.
Notably, it would be desirable to provide such a sensor, which could feature a better light sensitivity, while keeping satisfactory color sensitivity and limiting the risk of chromatic aberration appearance.